1. Field of Technology
The present invention relates to a printing apparatus, a printing system, and a printing control method for printing a background image such as a watermark on a receipt along with print data sent from a host apparatus.
2. Description of Related Art
Technology for printing a background image of a watermark on paper is known from the literature and disclosed in for example, Japanese Unexamined Patent Appl. Pub. 2003-220748.
Watermarks are printed to indicate that a document is confidential by printing a particular image (mark) repeatedly at regular intervals on a receipt. For example, a watermark may be printed as a store logo, at regular intervals on a receipt issued at the point of sale. An example of a receipt with a watermark WM is shown in FIG. 11A.
The background image is typically not printed by the local printing apparatus (receipt printer) on this type of roll paper used for printing receipts. Instead, as is shown in FIG. 11B, the pattern or mark used as the background image is preprinted at the factory and the paper is then wound into rolls and supplied as preprinted rolls for use in the store. A receipt printer then prints the transaction information and other print data at the point of sale on roll paper having a preprinted background pattern for issuance as a receipt. The purpose of printing the background image on the local printing apparatus instead of using preprinted roll paper is to print transaction data superimposed on watermark data on a receipt, that is, so that the same type of sales receipt having a watermark in the background can be issued by the receipt printer without using preprinted roll paper. When the watermark is printed by the printer, the watermark is printed at a regular interval in the same way as on preprinted roll paper.
As shown in FIG. 11C barcodes (S1) and other data symbols are often printed on receipts today. When a barcode is printed over the watermark WM, the watermark can interfere with the ability to read the barcode. In addition, receipts are increasingly printed with a top logo TL containing the store name, address, and even a store logo at the top of the receipt, and other image data, such as product coupons, may be printed at other desired locations on the same receipt. If these images are printed over the watermark and thus overlap, the watermark the original image (the non-watermark image) may be illegible and detract from the appearance of the receipt.
The present invention provides a printing apparatus, a printing system, and a printing control method which prevents the loss of readability and visual appeal, caused by superimposing the printing of specific print data on a watermark.